Term
| What is the structure of an antibody? |
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Definition
| Heavy chain makes up the whole of the Fc region and part of the Fab region. Light chain pairs with the heavy chain. Variable region binds to antigen. Disulphide bonds allow for max flexibility. |
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Term
| What are the four principles of clonal selection? |
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Definition
1. Each lymphocyte bears single type of receptor with unqiue specificity
2. Interaction btween a foreign molecule and lymphocyte receptor capable of binding leads to activation of lymphocyte
3. Daughter cells are identical to activated parent
4. Cell bearing receptors specific for self molecules are deleted from repertoire. |
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Term
| What 3 things do antibodies do? |
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Definition
1. Neutralise toxins and viruses
2. Help phagocytose pathogens
3. Destroy bacteria and viruses |
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Term
| What 3 tricks does the body have for increasing antibody repertoire to 10^11 with only 30000 genes? |
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Definition
1. Gene recombination
2. Adding of random base pairs when linking coding ends
3. Affinity maturation |
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Term
| What is gene recombination? |
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Definition
| Only occurs in lymphocytes where RAG forms hairpin complexes, cleaving at 23bp and 12bp and eliminating genes to form new combinations. |
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Term
| What's the problem with affinity maturation? |
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Definition
| Selectively mutates antibodies to improve their affinity for antigens so can lead to dangerous mutations e.g. leukemia |
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Term
| What four bonds can antibodies use to bind an antigen? |
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Definition
| Electrostatic forces, hydrogen bonds, Van der Waal's and hydrophobic forces. They recognize 3D structure, not type of molecule |
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Term
| What enzymes are involved in adding random base pairs? |
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Definition
| RAG proteins bring RSS together to generate hairpins. Nuclease opens DNA. TdT adds random base pairs Exonuclease and ligase repair DNA |
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Term
| What genes are involved in light and heavy chain formation? |
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Definition
| V (variable), D (diversity) and J (joining) |
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Term
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Definition
| Most abundant and common antibody found in serum. Characterised by y heavy chain and high affinity. Affinity and concentration increase with vaccine. Dimer of 2 heavy/2 light chains. |
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Term
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Definition
| Polymeric and secreted from mucosal surfaces e.g. gut. Characterized by a heavy chain. |
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Term
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Definition
| Similar to IgG in structure (a immunoglobin) and binds to special receptors on mast cells (which contain histidine) and eosinophils. Activates inflammation. |
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Term
| How is the Fc region encoded for? |
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Definition
| AID induces breaks nicks in DNA, stimulating dsDNA repair system which kicks out genes in formation of excision circle. |
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Term
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Definition
| Forms pentameric structure with 5 antibody dimers held together by J chain. First to be produced in response to stimulant. Low affinity but lots of binding sites. |
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Term
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Definition
| Caused by neurotoxin produced by Clostridium tetani. Inhibits GABA or glycine release, leading to excitation of neuroaxon and unrestrained muscle spasms. |
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Term
| What is the influenza virus? |
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Definition
| Airbourne transmitted through aerosols. Rapidly evolving and can spread quickly through animals. Haemagglutanin (HA) bind to receptors on epithelial surface of lungs. |
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Term
| What are the steps of phagcytosis? |
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Definition
1. Bacterium coated with IgG
2. C3b binds to CR1 and antibody binds to Fc receptor, leading to phagocytosis
3. Macrophage membranes fuse, creating a phagosome
4. Lysosomes fuse with these vesicles, delivering bacteria-degrading enzymes. |
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Term
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Definition
| Have receptors for IgE. When IgE binds preformed granules containing histamine/cytokines are released, causing inflammation. |
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Term
| What are the four stages of antibody-dependent cell-mediated cytotoxicity (ADCC)? |
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Definition
1. antibody binds antigens on target cell surface.
2. Fc receptors on NK cells recognize antibody.
3. Cross-linking of Fc receptors signals for NK to kill target cell
4. Target cell dies by apoptosis. |
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Term
| What is compliment mediated cell lysis? |
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Definition
| An enzymatic pathway which leads to cellular destruction. Need just single IgM molecule for C1 protein to bind whereas you need two IgG.. Leads to protein production which forms pore in membrane. Lesions initiate lysis of cell. |
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Term
| What examples have we got of polyclonal antibodies being used to protect against toxins? |
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Definition
| Snake venom antibodies produced in sheep or horses and given to humans. Trastuzamab (Herceptin) is monoclonal antibody used to treat breast cancer by blocking downstream signalling. |
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Term
| How are monoclonal antibodies produced? |
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Definition
| Developed by Cesar Milstein and Kohler 1975; mouse injected with antigen, injected with furthur antigens, stimulating somatic hyper mutation. Fuse B cells with immortal myeloma cells to produce monoclonal hybridoma. |
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